Polycrystalline cubic boron nitride (PCBN) tools are excellent machining and milling tools. This allotropic crystalline form of boron nitride is very similar to diamond. Its crystals are obtained at a high temperature and pressure. These crystals have the same hardness as diamond. They are used for machining cast iron, tool steel, superalloys, and ceramic materials. PCBN has also gained acceptance in the friction stir tool industry.
PCBN is one of the hardest materials known to man. The grit of a single layer of c-BN has an abrasive concentration of up to 1.1 carats per cm3 of coating volume. The abrasive particles are sharp, superhard, and ensure maximum cutting performance. For profile grinding applications, a high concentration of abrasive particles is desirable.
CBN crystals are formed at pressures between 3.45 and 6.2 MPa. They are stable under an inert atmosphere, and they can be used at temperatures between 1900 and 3700 degF. A CBN passivation layer prevents further oxidation. In addition to preventing further oxidation, the passivation layer dissolves in water.
Resinoid bonded diamond and cBN grinding tools have different grit sizes. Ed mill sharpener The grit size is the equivalent of US mesh size. There are also special products for certain machining applications. One such product is the BT-150H. This wheel is specially designed to grind radii on standard inserts and angles on special turning tools. However, this wheel can also be used for polishing.
Diamond and CBN tools can be produced in a variety of shapes. For example, there are form grinding wheels, electroplated diamond and cBN tools, and sintered polycrystalline cBN. The latter are fabricated in a similar manner as diamond tools.
Electroplated diamond and cBN tools have good cut-off and surface finishing properties. They are a cost-effective alternative to conventional diamond and cBN tools. If the abrasive coating is not properly adhered, the tools can chip and degrade. As a result, they are best suited for smaller batch sizes, precision machining, and other demanding applications.
Resinoid bonded wheels are also available. These have a dense bond. They offer better shape retention. Compared to conventional wheels, they also have higher rigidity and can be used to grind ceramics.
PCBN tools are often used for machining ferritic steels, austenitic stainless steels, and nickel-based alloys. When paired with a machine tool, these tools can achieve high removal rates. They can be easily chipped, though, and they are not recommended for interrupted cutting. Moreover, they are not stable at higher temperatures.
Both types of grinding tools are effective for a wide variety of machining applications. The diamond / cBN tool has long profile-holding qualities, enabling consistent workpiece quality. Using this combination of abrasives can save on thermal damage to the workpiece, and it can even increase its life. Choosing the right tool is critical to its successful operation.
Another factor that can impact the effectiveness of a PCBN or diamond tool is the tool’s speed. Rigid, high-speed tools require a powerful machine. They also require a low eccentricity spindle, which minimizes tool fracture. Ideally, the recommended cutting speed is below the maximum speed of the tool.